Stencil duplicating inks



Patented Aug. 16, 1949 a 7 2,479,031 STENCIL'DUPLICATING nks Thomas SeaLChambers Florence,

Company,

Chicago, 111., assignors Chicago, 111., a corporationoi Illinois.

and Robert 'llhonipson .toA. B. Dick No Drawing. --Application'September 18, 1948, Serial No. 49,994 I p 1 This invention especially. to stencil; duplicating inks .;for use with rotary stencil duplicating machines or for other stencilling operations wherein ink-is transferred through a stencil to an impression;medium.,

Stencil duplicating inks. are unlike other inks in the sense that certainrphysical. characteristics are demandedof the inkto function properly in the duplicating machine to produce copy. quality of uniform and acceptacle character. Eunc: tionally, the ink is supplied inv continuous fashion to anink-pad otherlikereservoir or distributing medium, anclafter uniform. distribution therein, it is transmitted through the stencil openings to the impression medium, chiefly bygforces developed at the point of contact between the; rotating cylinder and the impression roller Drying generally occurs by absorption of. thevehicle or carrier into the pores or interstices between the fibers ofthe paper. S omeoi the characteristics by which stencil duplicating inks are distin llished are setiorth below: v 3 1. Sufficient. flow of a desired. character is necessary 1 to enable the ink. to distribute: itself quickly and uniformly throughout the ink pad and to efiect satisfactory transmission through .the stencil tothe impression mediumn Not so much flowis, demanded as .:willcause the fink to drip or. runfrom the inkvpad, or to; flood the stencil, whereby undesirable copy is obtained. In the event that the flow'is insufiicient,.ink distribution inthe pad and transmission through the stencil are such as to produce copy of variable and undesirable characteristics. Viscosity is.used as a measure of certainfiow characteristics. Yet, we find it'impractical presently. to define the desired flow characteristics of inks rigidly and exclusivelyinthe terms. of viscosity. The optimum viscosity'valuesvary widely according .to the materialsof which the ink is formulated and the 1 '19 c n. (clfiot 2651 relates tojnk; compositions and instrument by which. the measurements are made 2. The ink composition should be quick drying when applied to impression paper; otherwise, j it would be necessary to resort andcostly practices-in order. to handle the copy within a reasonable timeand eliminate setofi. The commonest deviceto cope-with this problem is the practice'of sl'ipsheeting; that is,,inse rti ng interlayer sheets between successive-I copies as they are duplicated. viated to a limited extent by using as the impression medium highly absorbent paper which rapidly'distributes the vehicle butmakes it prac tically impossiblefto obtain sharply defined copy because of feathering of theink.

3. The drying characteristics should not be such as to causeprem'ature hardening of the ink on the pad or clogging of; the stencil openings.

These, objectionable 1 features .which ordinarily to special. devices The problem may be allecause poor copy are minimized or substantially preventedby the use of relatively slow drying inks. .Slow drying i ks, remain in such condition that ink removal iromthe stencil, ink pad, or machine parts may be effected in a simple manner. The combination of characteristics. calling for quick drying on the impression medium, on the'one l1and,.and slow drying on the pad, on the other hand, is difiicult to achieve. 7 v

. fl. A. suitable ink should be sulficientlystable to minimize, or eveneliminate, inadvertentsepara-v tion of ingredients, prior to use or while in use, such as might lead-tooperating difficulties. The tendency of pigments to-rearrange themselves in non-uniform. distribution and the tendency of emulsions, when used, to break are constant sources of such operating d'ifficulties, causing clogging of the inkpad, stencil orcylindenand making it practically impossible to obtain copy of acceptable quality.

5. An ink composition for use with stencil duplicating. machines should be nonrcorrosiv'e to themachine parts. It. should be safe to handle, easy to manufacture, and have good shelf life.

6. The ink should not give show-throng that is, there should be little visibility of the copy from. the opposite side .of the impression paper.

It should not' g ive an oily or colored outline or .halo.

7. Itis which, after transferto theimpression medium, is 'relativelyresistant to moisture, and a wide variety of solvents, greases, chemicals, and the like. It should be resistant, thereforeto wetting, perspiration developed by the hands, and various organic and inorganic materials present in processes, products, and apparatus with which duplicated material might come in contact.

Ink, compositions capable of meeting the majority, of these characteristics have been the subject of considerable research since the advent of stencil duplicating machines in the latter part of the nineteenth century. Actually, little change has taken place in stencil duplicating ink formulations over and above those initially developed. The earlier stencil duplicating inks were pigmented oil-base compositions containing as much as 80,percent and som-etimes 'percent oil, which were mostly non-drying oils, such as castor oil, cocoanut oil, andthe like. Often a. binder, such as rosinfwas; incorporated to improvethe viscosity and other characteristics of the ink." In order .to effect solution of thebinder, a solubilizing agent, such as a rosin oil, was often'ncorporated. These inks were burdened by the fact that the presence of the" oils; and especially the non-drying oils, which functioned as the pigments, caused a highly objectional degree of setofi and smear, unless special devices were used inhandling the impression medium.

desirable, when possible, to have an ink V the. carr er orjvehiclef for the ink. From the standpoint of economics, past experience has shown that natural fats and. oils nomical formulation of oil-base inks.

In attempting to improve oil-base inks, emulsion inks were subsequently developed. Stencil duplicating inks of the oil emulsion type very often contained less oil to relieve some of the described objectional features of oil-base inks but new problems were presented which inhibited their utility in actual practice. The emulsion inks presented an operating problem because they often separated before or while in use, whereby the ink pad or the stencil or both became clogged to prevent uniform distribution of the ink and complicated the production of good copy. In addition, the inner phase of the emulsion frequently 'lcontained sulfonated glycerides which were corrosive to elements and machine parts associated therewith.

It is an object of this invention to produce a stencil duplicating ink which overcomes the objectionable features of prior inks and meets substantially all of the desirable characteristics of a gOOd stencil duplicating ink.

'Another object is to produce a stencil duplieating ink constituted primarily with miscible ingredients to minimize the danger of separation which might impair the quality of the ink or its function in the duplicating machine.

A further object is to produce a. stencil duplicating ink which is substantially free of oils whereby fast drying and good copy are obtained without the objectionable features of show-through and halo. 7

A still further object is to produce a stencil duplicating ink which may be used with relatively non-absorbent paper stock or with hard and highly finished surfaces on the impression medium, materials which were incapable of use with prior stencil duplicating inks.

Another'object is to produce an ink of the type described which is quick drying to enable handling almost immediately after duplicating without fear of setoif or smearing and which, after drying, becomes insolubilized to water to the eX- tent that it is unaffected by moisture, high humidity, solvents, greases, oils, hydrocarbons, and the like.

Another object is to produce a stencil duplieating ink which is substantially non-corrosive, and simple, easy, and safe to manufacture and handle.

An object of this invention is to produce a water-base stencil duplicating ink wherein water comprises the principal diluent and carrier and is combined with other substances adapted to impart color, body, penetrability, drying, and insolubility characteristics desired in a stencil duplicating ink.

These objects are accomplished according to our invention by formulating a water-base stencil duplicating ink in which water comprises the major diluent and functions primarily as the carrier or vehicle for the tinctorial matter. The desired body and flow of the desired character is derived from the use of a cellulose derivative which is miscible with the diluent to form a stable, non-corrosive solution that is safe to handle and easy to manufacture. The cellulose derivative not only imparts bodying character- 7 are frequently and unpredictably in short-supply,- and this impairs suitable standardization or ecoresinous materials are 'bodying agent when transferred 4 istics to the composition but also functions as an adherent base upon drying to permit duplicating on non-absorbent and highly finished paper stock. When desired, a water-soluble reactant may be incorporated to insolubilize the resin or to the impression medium.

As the tinctorial agent, use may be made of water soluble dyes, such as nigrosine dye of the type Nigrosine WSJ. Use may also be made of other water soluble acid and basic dyes, such as triphenylmethane, rhodamine, thioflavine, and auramine dyes, or sulfonated triphenylmethane, quinone-imide and xanthone dyes. Representative of the acid dyes which have been successfully used are the materials marketed by Calco Chemical, 'a Division of American Cyanamide Company, under the trade name Calcocids, which include the mono-, di-, and tri-sodium sulphonate derivatives of the nitro, azo, pyrazoline, quinoline, triphenyl-methyl, diphenylnaphthylmethane, azine, xanthone and anthroquinone groups. To a limited extent, the azo dyes may also be incorporated as the tinctorial agent in ink formulations of the type described. Instead of dye compounds, dispersions of inorganic pigment may be used in which the pigments may comprise carbon black, lamp black, malachite green, iron blue, cadmium yellow, and the like. The amount of dye in the ink formulation depends on the chemical nature of the coloring material used. Some dyes are capable of imparting sufiicient color to lend legibility to the copy when little is used, while with others, it is necessary to use higher concentrations of dye to secure the desired eifect. The lower limit of the dye concentration, therefore, is determined by its tinctorial strength which varies widely from compound to compound. The upper limit often is influenced by solubility factors or by the eifect of the dye on other ingredients of the ink composition, as, for example, in causing gelation of the resinous material. We have found that 3 to 7 percent Nigrosine WSJ is suitable for these water-base inks. The amounts of other dyes may be more or less according to their characteristics, as pointed out above. When pigments are used, it is often desirable to use concentrations ranging from 3 to 15 percent or more of the ink composition when calculated on a weight basis.

By the phrase cellulose derivative miscible with water it is meant to include cellulose ethers soluble in water or dilute aqueous alkaline solutions, such as the hydroxylated cellulose ethers in which there are suificient hydroxyl groups to influence solubility in aqueous medium. Among the water soluble ethers of cellulose which find excellent use in stencil duplicating ink formulations of the type described are the hydroxylalkyl celluloses, such as hydroxyethyl cellulose. Use may also be made of the partially alkylated cellulose ethers, such as a medium viscosity methyl cellulose or ethyl cellulose having less than 19 percent ethoxy groups. We have found that the water soluble salts'of carboxy methyl cellulose, such as sodium or ammonium carboxy methyl cellulose, may also be used. The amount of water soluble cellulose ether derivative required to impart the desired flow characteristics varies according to the degree of polymerization or the average molecular weight of the cellulose ether derivative, the degree of alkylation, the groups of which the cellulose ether is constituted, and to a lesser extent according to the substances by which the taken into solution. In

' the resinous material upon drying,

emote? actual practice,- sufiicient body in the ink composition is .derived for use with present duplicating machines when the composition contains2 to IO-percent 'hydroxyethyl cellulose (Cellosi-z'c) but more or less maybe used. when desired. Since the bodying capacity of suitable. resinousmaterials varies: according .to their. molecular construction, it is: more. expedient to. define :the limitations asito theramounts ofrbodying agents in accordance with their resulting influence on flow characteristics. This can'be' determined by ordinary .viscosimeters: asithe: measurement corresponding to a .viscosity' of. aboutz35. to 150 seconds measured by a Stormer viscosimeter operating with a standard cup without a center bailieat-ZO" C. under a'200 gramloacl. Of course, it will be understood that as the requirements of duplicating. machineschange .irrthe course of developments in the art, the"viscositylimitations and, therefore; the amount of bodyingv agent may change accordingly without dpartingfrom the invention. i. g

A .valuable'feature ofthis invention resides in thefactrthat the water soluble cellulose ethers of the" type described are constituted. withhydroxyl groups capable of reaction: with an aldehyde to insolubilize the resinousmaterial. Similarity exists' between the possible-reaction and that of the acetal reaction between carbonyl and hydroxyl groups; When use is' made of an aldehydic substance capable of latent r'eaCtlo-nto insolubilize excellent stability and shelf life of the ink composition are secured before duplication; and after transfer to the impression medium,- the desirable characteristics of quick drying. and resistance to moisture, and many solvents, greases, o'ls, hydrocarbons, and the like are secured; One such latent alde hydic substance is glyoxal. andanother, less reactive and COllSC-IClLlGIltl-YUSGd in greater amounts, is pyruvic aldehyde. Either of these: substances may be referred to as bifun-ctiorial carbonyl compounds, which, in the'presence'of catalyst or upon drying, are capable of the acetal reaction. Each has at least one'iunctionalaldehyd'e group. Insolubili-ty may result irom the elimination'of hydroxyl 'groupsjthe formation of hemi-acetals, or the cross linking of cellulose molecules, as is typical of the acetals. Insolubilization may also be derived, even in'the absence of glyoxal, 'from the loss or ammonia in the event that-'an'amrnonium salt of a carboxy cellulose ether is used. 0.25 to 3.0 percent of glyoxal based upon the weight'oi the inkcomposition is usually suflicient, andas much as '7' percenthas been used, but best results are secured when the cellulose. resin and aldehyd'eare present'in theratio of about 2 to 10 parts by weight of the resin to 1 part of the aldehyde.

In order to increase the penetrability into the impression paper and in order to improve the characteristics of the ink with respect to distribu- Percentage tion through the ink pad and stencil, a wetting agentmay be added to I able wetting agent maybe selected from the group consisting of the dioctyl esters ofsodium sulfosuccin'ate (Aerosols), quaternary ammonium salts (Tritons) substituted aromatic sulfonates (Duponols), dibutylphenol sodium disulfonates '(Areskelene) sulfonated ethers (Tensol), and the like. Less than two percent of the wetting agent ordinarilyis sufiic'ientto impart the desired wetting characteristic,- although more may be used when desired. g V 7 i v In order'tominimize' the tendency of the inks the composition; A suitagent. Whenmore is Percentage in any order since to dry toorapidly. before transfer v to' the impression: medium. even undenconditions of :high tem: perature or lowhurnidity, in order: to provide an adherent baseiaiter the water: has been removed which: is; flexiblezand hasrdesirable physical char.- a'eteristics, and toaimprove" wet strength and. mois: ture 1 resistance; a non-volatile organic-liquid compatible .with th-e solution of the water. soluble cellulose: .ether is l'added. These properties are derived by the addition of polyhydric alcohols, such glycerin'e; ethyleneglycol, diethylenglyc'ol, p'olyglycols', and: the like: An important and mostbeneficialiphenomenon is derived from the use oi polyhydric alcohols in ink formulations of the: type described. .Polyhydric alcohols improper. amounts appear to increase the stiffness, that isimp'art afalse body to the inkto the extent that 'free flow is apparently reduced. By their-use leakageirom the 'cylinder or inadvertent flow of the inkcomposition from the pad or stencilffs noticeably reduced. Actually, theapparent increase-d stifihess is not measurable by a' viscosimetereperating highrates of shear. As aresult, it is not apparent upon transfer of theinl: to the impression mediumbecause flow under high shearing rates' -results -when*the ink is forced'through the stencil-Q The polyhydric-abcohols may react with the aldehyde-conjointly with the cellulose etherderivative totorrn acetals and cross-linkages. In specific application's, amounts ranging from 1 to 25 percent by weight of ethylene glycol have been successfully used with compositions constituted with hydroxyethyl cellulose of medium viscosity as the bodying 7 used, thereis 'a'tendencyto disturb the colloidal state-of the ingredients of the ink composition. Corresponding amounts of other polyhydr'ic alcohols may be used. The upper limit of concentration of any selected polyhydric alcohol or combination of polyhydric'alco hols with the same or other types of suitable cellulose ethers-isthat which causes gelling or other undesirable disturbance of the colloidal state of thesystern. V Thedollowing examples will illustratewaterbase stencil duplicating inks embodying features of our inventionp a Q Example I Material Water. a

. Nigrosine WSJ (water soluble dye).

Hydroxycthyl cellulose c. p. s. in 10% aqueous solutio i a l Aerosol OT.

Ethylene glycol.

- Glyoxal.

H sw s a-. mo o obcn Example-II H1 Material 7 4 OOOOOON Glyoxal and pyr'uvic aldehyde are normally'i nc orporated as a 30 percent water solution; however, the amounts 'designated in the above. examples refer to the dryweight of the free aldehyde. While the materials may be combined they are generally miscible one with the other, it is usually preferred to prepare the solution of resin in the liquid vehicle first. The above formulations have a viscosity within the range of 50-100 seconds, as measured by a Stormer viscosimeter of the type previously described. By comparison, viscosities of suitable oil base stencil duplicating inks may be about 400-500 seconds and many suitable oil base emulsion inks may have viscosities of about 250-350 seconds.

When water insolubility is unimportant, the bifunctional carbonyl compound may be omitted. In the event that the insolubilizing agent is omitted, the ink is not entirely devoid of moisture resistance because the polyhydric alcohols function, to an extent, as a protective agent for the inks and they impart some degree of water resistance.

By the use rof our new and improved stencil duplicating ink, drying takes place at a speed which is beyond that heretofore contemplated for stencil duplicating inks, making it possible to handle the copy immediately. It is possible to eliminate setofi without the costly and cumbersome technique of slipsheeting. It is possible to duplicate on hardstocks and highly finished impression media and still handle the work immediately. The ink produced by this invention dries rapidly on bond, ledger, card, or enamel stock, papers which have heretofore not been suitable for widespread use with stencil duplicating machines.

There are no materials present in such quantity to cause undesirable "show through or halo. This is because the present carrier and diluent is water which may be completely eliminated from the impression medium and is not resident as are the oils of prior duplicating inks.

It will be evident that other important advantages are derived from the use of water-base stencil inks including the elimination of possible separation of the ink in use or prior to use because the ink composition is stable; simplification in the processes of cleaning the machine and stencil by the use of a simple water rinse as effected by a dip or spray because the ink composition before transfer to the impression medium is readily soluble in water and many of the common solvents; self-sealing characteristics derived from the use of the polyhydric alcohol and cellulose ether derivative to reduce the tendency of the inks to drip inadvertently or leak from the container or cylinder because of the high body of the ink composition in the free statej simplicity in ink manufacture because preparation is eifected by solution which eliminates grinding or other tedious means for incorporating the colors and resinous material.

It will be understood that the basic substances may be prepared for marketing in concentrated or dry form to be diluted at the station of use with water before filling the ink container. It will further be understood that other miscible solvents may be partially substituted for the water as the diluent or diluting substance, such, for example, as the lower alcohols and the like. In addition, it will be understood that numerous substitutions may be made in the materials and their amounts without departing from the spirit of the invention, especially as defined in the following claims.

We claim as our invention:

l. A stencil duplicating ink comprising an aqueous composition consisting essentially of water as the diluent, a tinctorial agent to impart claim 3 in which t legibility to the copy, a water soluble cellulose derivative selected from the group consisting of cellulose ethers and cellulose esters having water solubilizing hydroxyl groups and alatent aldehyde selected from the group consisting of glyoxal and pyruvic aldehyde.

2. A stencil duplicating ink comprising an aqueous composition consisting essentially of water as the diluent, a tinctorial agent, a water soluble cellulose ether for bodying the composition and for operating as an adherent base upon drying, a liquid polyhydroxy alcohol compatible with the solution of cellulose ether in diluent, and a wetting agent.

3. A stencil duplicating ink comprising an aqueous composition consisting essentially of water as the diluent, a tinctorial agent, a water soluble cellulose ether for bodying the composition and for operating as an adherent base upon drying, a liquid polyhydroxy alcohol compatible with the solution of cellulose ether in diluent, a wetting agent, and an aldehyde selected from the group consisting of 'glyoxal and pyruvic aldehyde.

4. A stencil duplicating ink'comprising more than'50 percent water as the diluent, from 3 to percent of a tinctorial agent, from 1 to percent of a water soluble 'hydroxylated cellulose ether, from 1 to 25 percent of a liquid polyhydroxy alcohol compatible with the solution of the cellulose ether and water which in the prescribed amount does not harmfully afiect the structure and stability of the colloidal composition, a wetting agent, and an aldehyde selected from the group consisting of glyoxal and pyruvic aldehyde.

5. A stencil duplicating ink comprising more than 50 percent water as the principal diluent, 3 to 7 percent by weight of a water soluble dye, 2 to 10 percent of hydroxyethyl cellulose, 3 to 25 percent of ethylene glycol, 0.5 to 2.0 percent of a wetting agent, and .25 to 3.0 percent of an aldehyde selected from the group consisting of glyoxal and pyruvic aldehyde.

6. A stencil duplicating ink comprising an aqueous composition consisting essentially of water as the major diluent and carrier, a tinctorial agent, a polyhydric alcohol, a cellulose ether derivative soluble in aqueous media of the type Water and dilute alkaline solutions and present in sufiicient quantity to provide a body to the ink composition corresponding to a viscosity of 35 to 150 seconds measured by a Stormer viscosimeter operating with a standard cup without a center bafiie at 20 C. under a 200 gram load.

'7. A stencil duplicating ink as claimed in claim 5 1 in which the cellulose derivative is hydroxyethyl cellulose.

8. A stencil duplicating ink as claimed in claim 1 in which the cellulose derivative is ethyl cellulose having less than one-third of the hydroxyl groups ethylated.

9. A stencil duplicating ink as claimed in claim 1 in which the cellulose derivative is methyl cellulose.

. 10. A stencil du plicating ink as claimed in he cellulose ether is hydroxyethyl cellulose.

11. A stencil duplicating ink as claimed in claim 3 in which the cellulose ether is methyl cellulose. 12. A stencil duplicating ink as claimed in claim 3 in which the polyhydroxy alcohol is ethylene glycol.

13. A stencil duplicatin 3 in which the poly glycol.

14. A stencil duplicating ink as claimed in claim g ink as claimed in claim ydroxy alcohol is diethylene present in an amount 4 in which the aldehyde is 2-10 parts by ranging from 1 part aldehyde to weight cellulose ether.

15. A stencil duplicating ink as claimed in claim 4 in which the aldehyde is present in an amount ranging from 0.25-7.0 percent by weight.

16. A stencil duplicating ink as claimed in claim 4 in which the cellulose ether is hydroxyethyl cellulose and the aldehyde is present in an amount ranging from 0.25-3.0 percent by weight.

1'7. A stencil duplicating ink as claimed in claim 4 in which the tinctorial agent is a water soluble dye.

18. A stencil duplicating ink as claimed in claim 4 in which the low aliphatic polyhydroxy alcohol is diethylene glycol.

19. A stencil duplicating ink as claimed in claim 4 in which the cellulose ether is hydroxyethyl cellulose, the polyhydroxy alcohol is diethylene glycol and the aldehyde is glyoxal.

THOMAS SEAL CHAMBERS.

ROBERT THOMPSON FLORENCE.

REFERENCES CITED The following references are of record in the file of this patent:

OTHER REFERENCES American Ink Maker, June 1945, pages 21. 22 and 23. 

